Many electrical products use a fan as the main heat sink. The fan increases the rotational speed thereof to reduce the system temperature when the system temperature is high. The fan maintains a fixed rotational speed when the system temperature is lower than a specific temperature.
Typically, a DC fan is used to avoid electrical system damage due to high temperature. The typical DC fan has a fan protection apparatus. This fan protection apparatus can force the DC fan to stop work when the fan meets an abnormal situation. For example, a foreign material locks the DC fan. After a specific time interval, the protection apparatus restarts the DC fan and checks whether or not the DC fan is still locked by the foreign material. The protection apparatus forces the DC fan to stop again if the abnormal situation still exists. Then, the protection apparatus restarts the DC fan again after a specific time again passes. In other words, the typical fan protection apparatus performs a repeating loop of stopping the fan and restarting the fan to avoid the abnormal situation.
However, the typical fan protection apparatus and method have many problems. First, the conventional fan protection apparatus and method lacks a standard for determining whether the abnormal situation can be eliminated. Therefore, the stop/restart loop will be continually performed if the abnormal situation still exists in the fan, which may break the fan. In other words, the DC fan will not be shut down even though the abnormal situation cannot be eliminated. Second, a larger restart current is required to start the DC fan. The larger restart current causes an unstable electrical system in the stop/restart process.